Drawdown is a temporary solution.
It's not whether but when to annuitise

The objectives for most drawdown investors should be to maximise investment and income growth in the early years and security of income in the later years. Drawdown, by its very nature, will become progressively less suitable as you get older and it is important to consider drawdown exit strategies from age 70 onwards. 

It is necessary to consider exit strategies because as you get older, it becomes much cheaper to buy an income for life (an annuity).

The graph below shows the approximate extra annual return currently available for men depending on the age at which an annuity is bought.

Accordingly, it becomes increasingly difficult to produce investment returns that compensate for the absence of increasing annuity returns.